In conventional windows, the glass pane—which today is usually laminated insulating glass—is generally fastened in a frame. The frame lies around the periphery of the glass pane in the plane of the glass pane, and the glass pane is fixed (“blocked”) in the frame with blocks pushed in between the frame and the peripheral sides of the glass pane. To ensure that the fixation is as free of force as possible, the load-bearing blocks (“supporting blocks”) in the case of vertical glass are usually made of rigid plastic or hardwood, and the blocks that have less load on them (“spacer blocks”) are made of a softer elastic material.
When glass panes are used for glazing on façades, e.g., double façades or element façades, or in the interior, e.g., for inner walls or elevator shafts, the fastening usually has to be as inconspicuous as possible, almost invisible, for which reason a frame construction such as is used for windows is unsuitable. Instead, today the glass panes for glass façades, glass sidings, and even glass rotating elements and glass sliding elements are usually fastened to a substructure lying behind the plane of the glass pane, e.g., in mullion/transom construction. Remaining narrow joints between the individual glass panes are provided either with joint sealant or with cover moldings. In order to be able to replace the individual glass panes separately, the fastening must be detachable.
On the one hand, the glass pane can be fastened to the substructure using point mounts with bolts that pass through the glass pane, e.g., at the corners. Such point mounts leave especially narrow joints between adjacent glass panes, since the joints can be designed merely as expansion joints, however require an elastic connection between the bolt and the hole in order, e.g., to compensate for the thermal expansion of the glass pane. Furthermore, the glass panes must have holes drilled through them, structurally weakening them precisely at the points of highest load—the fastening points.
On the other hand, line mounts are used, which involve clamping every glass pane against the substructure, e.g., by cover moldings that are screwed through the joints to the substructure and that simultaneously come in contact with the outside edge of the glass pane. However, especially in the case of large glass panes, this clamping requires large forces, and thus solid cover moldings that are clearly visible from outside. This also puts the glass panes under high stress.
Alternatively, every glass pane can also be borne by rest strips that protrude from the substructure and can optionally be blocked between them, fixation of the glass pane to the substructure additionally requiring cover moldings that are screwed against the rest strips and that come in contact with the outside edge of the glass pane. In this variant, the glass panes are mounted largely free of stress, however wider joints and also outside cover moldings are required, limiting the design freedom for the glass façade.